1. Field of the Invention
The present invention relates to a cylindrical cutting blade, and a cutter head assembly including a main body which holds the cylindrical cutting blade and is rotated to machine a workpiece.
2. Discussion of Related Art
As an example of such a cutter head assembly, JP-A-10-58232 discloses a face milling or hobbing cutter used in a gear cutting operation in which a spiral bevel gear, a hypoid gear or other bevel gear having curved teeth is machined or cut in accordance with a so-called xe2x80x9cforming method (non-generating method)xe2x80x9d or xe2x80x9cgenerating methodxe2x80x9d. This cutter includes (a) a disk-shaped main body which is to be rotated about its axis, (b) a plurality of cylindrical cutting blades and (c) a clamping device for fixing each cutting blade to the main body. The main body has a plurality of cutting-blade receiving bores and wedge-member receiving bores all of which have respective circular shapes in their cross sections. Each of the cutting-blade receiving bores is offset from the axis and extends substantially parallel to the axis, while each of the wedge-member receiving bores extends in a direction not parallel to the axis so as to intersects with the corresponding one of the cutting-blade receiving bores. Each of the cutting-blade receiving bores interferes with the corresponding two of the wedge-member receiving bores which are positioned to be spaced apart from each other in a direction in which the cutting-blade receiving bore extends. Each of the cylindrical cutting blades has a predetermined diameter which enables the cylindrical cutting blade to be fitted into the cutting-blade receiving bore, and a flat surface in its outer circumferential surface. The flat surface is parallel to the axis of the cylindrical cutting blade, and is formed by removing a portion of the cylindrical cutting blade which is located on one of opposite sides of the flat surface remote from the axis. Each cylindrical cutting blade further has, in its axially distal end portion, a cutting edge defined by an intersection of a flank face and a rake face which is constituted by the flat surface.
The clamping device includes a generally cylindrical wedge member which is fitted in the wedge-member receiving bore such that the wedge member is slidably movable relative to the receiving bore in the axial direction of the receiving bore, and a moving mechanism for moving the wedge member relative to the receiving bore in the axial direction. The wedge member has a positioning surface which is inclined with respect to the axis of the wedge member. When the wedge member is forwardly moved by the moving mechanism, the positioning surface of the wedge member is brought into abutting contact with the flat surface of the cylindrical cutting blade, for thereby holding the cutting blade in a predetermined angular position relative to the cutting-blade receiving bore while pressing the cylindrical cutting blade onto an inner circumferential surface of the receiving bore owing to a wedge effect. The cylindrical cutting blade is thus fixed to the disk-shaped main body. It is noted that the moving mechanism is provided by an externally threaded member and an internally threaded member which are held in engagement with each other. One of the externally and internally threaded members is rotatable relative to the wedge member.
This cutter head assembly disclosed in JP-A-10-58232 has a construction more simple than that of a conventional cutter head assembly, and an excellent capability to fix the cutting blades to the main body. However, the present inventors felt a need of further simplifying the construction, or further improving the capacity to fix the cutting blades to the main body.
It is therefore a first object of the present invention to provide a cutter head assembly which is further improved in simplification of construction and capacity to fix cutting blade or blades to a main body thereof.
It is a second object of the present invention to provide a cutting blade which is advantageously used in a cutter head assembly.
The above first object may be achieved according to any one of the following modes of the present invention, each of which is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate and clarify possible combinations of elements or technical features. It is to be understood that the present invention is not limited to the technical features or any combinations thereof which will be described for illustrative purpose only. It is to be further understood that a plurality of elements or features included in any one of the following modes of the invention are not necessarily provided all together, and that the invention may be embodied without some of the elements or features described with respect to the same mode.
(1) A cutter head assembly for cutting a workpiece, comprising:
a main body which is to be rotated about an axis thereof, and which has at least one cutting-blade receiving bore offset from the axis and extending from an axially distal end face of the main body toward an axially proximal end face of the main body, the main body further having at least one clamping-member receiving bore unparallel to the cutting-blade receiving bore and partially interfering with the cutting-blade receiving bore;
at least one cylindrical cutting blade each received in a corresponding one of the above-described at least one cutting-blade receiving bore and having a flat surface formed as a part of an outer circumferential surface thereof and parallel to an axis of the cutting blade, the cutting blade further having a cutting edge in an axially distal end portion thereof which projects from the axially distal end face of the main body; and
at least one cylindrical clamping member each received in a corresponding one of the above-described at least one clamping-member receiving bore and having a fitting portion and a cam portion, the cylindrical clamping member being fitted at the fitting portion in the clamping-member receiving bore, the cam portion having a cam surface whose radial distance from an axis of the fitting portion changes in a circumferential direction of the cylindrical clamping member,
wherein the cylindrical clamping member is rotatable about the axis of the fitting portion so that the cam surface is brought into contact with the flat surface of the cutting blade, for thereby pressing the cutting blade onto an inner circumferential surface of the cutting-blade receiving bore.
In the present cutter head assembly, when the cylindrical clamping member is operated to be rotated in a predetermined direction, the cam surface is pressed onto the flat surface of the cylindrical cutting blade, which surface is formed by removing a portion of the cylindrical cutting blade that is located on one of opposite sides of the flat surface remote from the axis. With the pressing contact of the cam surface with the flat surface, the cylindrical cutting blade is held in a predetermined angular position relative to the cutting-blade receiving bore while being pressed onto the inner circumferential surface of the cutting-blade receiving bore, so that cylindrical cutting blade is firmly fixed to the main body. The cylindrical clamping member is more simple in construction in which the fitting portion and the cam portion which are formed integrally with each other, than that of the clamping device of the above-described cutter head assembly disclosed in JP-A-10-58232. The simple construction of the clamping member leads to a simplification in the construction of the entirety of the cutter head assembly, making it possible to manufacture the cutter head assembly in a reduced manufacturing cost. The simple construction of the clamping member also enables the clamping member to be more compact in size, making it possible to increase the number of the cutting blades carried by the single main body of the assembly, without increasing the size of the main body. The increased number of the cutting blades leads to an increase in the amount of stock removed from the workpiece during one rotation of the cutter head assembly, resulting in an improved machining efficiency.
The present cutter head assembly provides another advantage that the cutting blade is prevented from displaced relative to the main body not only in a direction perpendicular to the flat surface of the cutting blade but also in the axial direction of the cutting blade, owing to the arrangement in which the cutting blade is firmly pinched or gripped by and between the clamping member and a portion of the inner circumferential surface of the cutting-blade receiving bore which is substantially opposite to the clamping member.
It should be understood that the direction of the rotation of the clamping member causing the cam surface of the clamping member to be pressed against the flat surface of the cutting blade may be suitably determined depending upon a direction in which a cutting resistance is applied to the cutting blade during a cutting operation. For example, where the cutting resistance as a resultant force includes an axial force component which forces the cutting blade in a direction away from the axially distal end face of the main body toward the axially proximal end face of the main body, it is preferable that the cam surface is brought into pressing contact with the flat surface of the cutting blade by rotating the clamping member in such a direction that causes a contact portion of the cam surface brought into contact with the flat surface, to be moved away from the axially distal end portion of the cutting blade toward the axially proximal end portion of the cutting blade. In this arrangement, when the cutting blade is forced in the direction away from the axially distal end face of the main body toward the axially proximal end face of the main body, a friction force acting between the cam surface and the flat surface is increased, whereby the cam portion of the clamping member is placed in a so-called xe2x80x9cself-locking statexe2x80x9d for holding the cutting blade against the axial force component of the cutting force.
On the other hand, where the axial force component of the cutting resistance forces the cutting blade in the opposite direction, i.e., in a direction away from the axially proximal end face of the main body toward the axially distal end face of the main body, it is preferable that the cam surface is brought into pressing contact with the flat surface of the cutting blade by rotating the clamping member in such a direction that causes the above-described contact portion of the cam surface to be moved away from the axially proximal end portion of the cutting blade toward the axially distal end portion of the cutting blade.
(2) A cutter head assembly according to mode (1), wherein the cylindrical cutting blade has a cutout formed in the outer circumferential surface such that the cutout extends in a direction parallel to the axis of the cutting blade and is diametrically opposite to the flat surface.
In the assembly according to this mode (2), when the cutting blade is forced by the cam portion of the clamping member in a clamping force direction that is perpendicular to the flat surface of the cutting blade, the cutting blade is brought into contact, at circumferentially opposite edges of the cutout rather than at a single portion of its outer circumferential surface which portion is precisely opposite to the flat surface in the diametric direction (which portion lies on a plane that is perpendicular to the flat surface and that contains the axis of the cutting blade), with the inner circumferential surface of the cutting-blade receiving bore. That is, the cutting blade is held at two portions of the outer circumferential surface which portions are circumferentially spaced apart from the above-described single portion in the circumferential direction, by the inner circumferential surface of the cutting-blade receiving bore. In other words, the cutting blade is held by two tangential planes which consist of respective two portions of the inner circumferential surface of the cutting-blade receiving bore and which are inclined with respect to the above-described clamping force direction, in respective directions opposite to each other. In this arrangement, a wedge effect is provided between the two tangential planes and the two potions of the outer circumferential surface of the cutting blade, whereby the cutting blade is prevented from being displaced relative to the main body not only in a first direction that is perpendicular to the flat surface of the cutting blade but also in a second direction that is parallel to the flat surface and that is perpendicular to the axis of the cutting blade.
In the above-described cutter head assembly disclosed in the Japanese publication in which the cylindrical cutting blade is held only at a single portion of its outer circumferential surface precisely opposite to the flat surface in the diametric direction, by the inner circumferential surface of the cutting-blade receiving bore, there inevitably exists a small gap or clearance between the outer circumferential surface of the cutting blade and the inner circumferential surface of the bore as viewed in the second direction, resulting in an undesirable displacement of the cutting blade in the second direction upon application of a force to the cutting blade in the second direction. This drawback is solved by the cutter head assembly according to this mode (2), as is clear from the above description.
(3) A cutter head assembly according to mode (1), wherein the cylindrical cutting blade has a second flat surface in addition to the flat surface as a first flat surface, the second flat surface being formed as a part of the outer circumferential surface of the cutting blade and parallel to the first flat surface.
The cutter head assembly of this mode (3) can be further easily manufactured while providing the same advantageous effects as the above-described assembly of mode (2). It is preferable that the second flat surface is formed to have such a circumferential width that permits a central angle of the second flat surface to be substantially 90xc2x0, for maximizing the advantageous effects provided by the present assembly. In this arrangement, the cutting blade is brought into contact at circumferentially opposite edges of the second flat surface whose central angle is substantially 90xc2x0 with the inner circumferential surface of the cutting-blade receiving bore. Namely, two pairs of the mutually contacted portions of the outer circumferential surface of the cutting blade and the inner circumferential surface of the bore are inclined with respect to the second flat surface by about 45xc2x0, in respective directions opposite to each other, for thereby reliably preventing displacement of the cutting blade in the second direction while avoiding considerable reduction in a rigidity of the cutting blade due to the reduction in the cross sectional area of the cutting blade.
(4) A cutter head assembly according to any one of modes (1)-(3), wherein the fitting portion of the cylindrical clamping member is provided by each of axially opposite end portions of the cylindrical clamping member, while the cam portion of the cylindrical clamping member is provided by an axially intermediate portion of the cylindrical clamping member.
In the assembly of this mode (4), the cylindrical clamping member is held, at its axially opposite end portions each of which provides the fitting portion, by the clamping-member receiving bore. This arrangement assures a sufficiently large rigidity of the clamping member, making it possible to press the cutting blade against the inner circumferential surface of the cutting-blade receiving bore with a large force.
(5) A cutter head assembly according to any one of modes (1)-(4), wherein the cam portion of the cylindrical clamping member consists of an eccentric cam portion which has a circular shape in cross section taken in a plane perpendicular to an axial direction of the cylindrical clamping member and which has an axis offset from the axis of the fitting portion.
In the assembly of this mode (5) in which the cam portion is provided by the eccentric cam portion, the cylindrical clamping member can be further easily produced.
(6) A cutter head assembly according to any one of modes (1)-(5), further comprising a clamping-member-removal preventing device which prevents removal of the cylindrical clamping member from the clamping-member receiving bore.
The removal of the cylindrical clamping member can be prevented by interference or engagement of the clamping member with the cutting blade. However, it is preferable that the clamping-member-removal preventing device is provided between the main body and the clamping member, for thereby preventing contact of the clamping member with a portion of the cutting blade that is other than the (first) flat surface, so as to further improve a reliability in the arrangement in which the cutting blade is fixed to the main body by the clamping member.
(7) A cutter head assembly according to any one of modes (1)-(6), further comprising an angular-displacement limiting device which defines a maximum angle over which the cylindrical clamping member is rotatable relative to the clamping-member receiving bore.
As described above, the direction of the rotation of the clamping member causing the cam surface of the clamping member to be pressed against the flat surface of the cutting blade is preferably predetermined depending upon the direction in which a cutting force is applied to the cutting blade during a cutting operation. In this respect, it is preferable that the angular-displacement limiting device is provided to prevent the cam surface from being pressed against the flat surface by rotation of the clamping member in a direction opposite to the predetermined direction.
(8) A cutter head assembly according to any one of modes (1)-(7), further comprising a limiting member which is fixed to the main body and which has an engaging portion in a distal end portion thereof,
wherein the cylindrical clamping member has an engaging groove which is formed in an outer circumferential surface of the fitting portion and which extends over a predetermined distance in a circumferential direction of the cylindrical clamping member, and wherein the limiting member is engaged at the engaging portion with the engaging groove.
In the assembly of this mode (8), the clamping-member-removal preventing device and the angular-displacement limiting device are provided by the cooperation of the limiting member and the engaging groove which are simple in constructions.
(9) A cutter head assembly according to any one of modes (1)-(8), wherein the cutting edge is defined by an intersection of a rake face and a flank face which are formed in the cylindrical cutting blade, and wherein the rake face is parallel with the axis of the cylindrical cutting blade.
In the assembly of this mode (9) in which the rake face is formed to be parallel with the axis of the cutting blade, a resharpening operation is easily carried out when the cutting edge of the cutting blade becomes dull. Namely, an original sharpness of the cutting edge is easily restored by regrinding only the flank face. Further, the rake face parallel with the axis of the cutting blade can be coated with a coating layer which is formed of titanium nitride, titanium carbide or other material in an electrodeposition process.
(10) A cutter head assembly according to mode (9), wherein the flat surface has an entire width as measured in a width direction perpendicular to the axis of the cylindrical cutting blade, and a recessed portion formed therein and elongated in a direction parallel to the axis of the cylindrical cutting blade, the recessed portion having a width as measured in the width direction, which width is smaller than the entire width, the rake face being provided by the recessed portion.
In the above-described cutter head assembly disclosed in the Japanese publication, when the rake face is modified for some reasons, the wedge member also has to be modified in accordance with the modification of the rake face which is provided by the flat surface of the cutting blade brought into engagement with the positioning surface of the wedge member. In the assembly of this mode (10) in which the rake face is provided by the recessed portion recessed toward the axis of the cylindrical cutting blade, the rake face can be modified as needed without having to modify the clamping member. Further, in the cutter head assembly disclosed in the Japanese publication, if the entirety of the rake face is coated with a coating layer, the positioning surface brought into engagement with the coated rake face is likely to be easily worn due to a high degree of hardness of the coated rake surface, possibly resulting in a reduced service life of the wedge member. In the assembly of this mode (10) in which the clamping member and the rake face does not interfere with each other, it is possible to avoid reduction in the service life of the clamping member even if the entirety of the rake surface is coated with a coating layer.
(11) A cutter head assembly according to mode (10), wherein the recessed portion is formed in a widthwise intermediate portion of the flat surface.
In the assembly of this mode (11), the cam surface of the cam portion of the clamping member is brought into close contact with widthwise opposite end portions of the flat surface which are located on respective widthwise opposite sides of the rake faces, for thereby making it possible to position the cylindrical cutting blade in a predetermined angular position relative to the cutting-blade receiving bore with higher accuracy and stability.
(12) A cutter head assembly according to any one of modes (9)-(11), wherein the rake face consists of a single surface.
In the assembly of this mode (12), the rake face is easily formed. It is noted that the rake face may consist of a flat surface or a curved surface which extends in parallel with the axis of the cylindrical cutting blade. The curved rake face makes it possible to form opposite side faces of a tooth slot of a gear with the single cutting blade, for example, in a hobbing operation.
(13) A cutter head assembly according to any one of modes (9)-(11), wherein the rake surface consists of a plurality of surfaces which intersect with each other.
In the assembly of this mode (13), the plurality of surfaces may include a first rake face which serves to actually cut the workpiece, and a second rake face which is unparallel and intersects with the first rake face. The second rake face may be parallel to the (first) flat surface, for improving an rigidity of the cutting blade and/or an efficiency of removal of cutting chips produced in a cutting operation.
(14) A cutter head assembly according to any one of modes (1)-(13), wherein the at least one clamping-member receiving bore includes a plurality of bores which interfere with respective portions of each of the at least one cutting-blade receiving bore, and wherein the respective portions are spaced apart from each other in an axial direction of the each of the at least one cutting-blade receiving bore.
In the assembly of this mode (14), the cutting blade is fixed to the main body more firmly and reliably than where the single clamping-member receiving bore is provided for each of the cutting-blade receiving bores.
(15) A cutter head assembly according to any one of modes (1)-(14), wherein the main body consists of a disk-shaped body whose center line lies on the axis about which the main body is to be rotated;
wherein the at least one cutting-blade receiving bore consists of a plurality of bores which are arranged in a circumferential direction of the disk-shaped body;
and wherein the at least one cylindrical cutting blade consists of a plurality of cutting blades which are respectively received in the plurality of bores.
(16) A cutter head assembly according to mode (15), wherein the plurality of bores are located on at least one circle whose center lies on the axis of the main body.
The assembly of this mode (16) is advantageously used as a face milling or hobbing cutter for cutting a bevel gear having curved teeth in accordance with a generating method or a forming method. The plurality of cutting blades commonly consist of a plurality of inside cutting blades and a plurality of outside cutting blades which are received in the respective cutting-blade receiving bores. Each of the inside cutting blades cuts the workpiece by a radially inner portion of its cutting edge which portion is closer to the axis of the main body than a radially outer portion of its cutting edge. Each of the outside cutting blades cuts the workpiece by a radially outer portion of its cutting edge which portion is more distant from the axis of the main body than a radially inner portion of its cutting edge. Where the above-described at least one circle consists of a single circle, namely, where the inside and outside cutting blades are received in the respective bores which are located on the single circle, the inside and outside cutting blades are formed to be different from each other in the arrangement of the cutting edge, such that the radially inner portion of the cutting edge of each inside cutting blade is positioned inwardly of the radially inner portion of the cutting edge of each outside cutting blade as viewed in the radial direction of the main body, and such that the radially outer portion of the cutting edge of each outside cutting blade is positioned outwardly of the radially outer portion of the cutting edge of each inside cutting blade as viewed in the radial direction of the main body. On the other hand, where the above-described at least one circle consists of a plurality of circles, e.g., a large circle having a comparatively large diameter and a small circle having a comparatively small diameter, the outside cutting blades are received in the holes located on the large circle while the inside cutting blades are received in the holes located on the small circle. In the latter case, the inside and outside cutting blades may be identical with each other in the arrangement of the cutting edge.
(17) A cutter head assembly according to mode (15) or (16), wherein the plurality of cutting blades consist of at least one pair of inside and outside cutting blades which are adjacent to each other in the circumferential direction, and wherein the cutting edges of the at least one pair of inside and outside cutting blades are arranged along at an involute of a base circle whose center lies on the axis of the main body.
The assembly of this mode (17) is advantageously used as a face hobbing cutter for machining or cutting a bevel gear having curved teeth in accordance with a generating method or a forming method. The cutting edges of all the cutting blades may be arranged along a single involute or a plurality of involutes of the base line whose center lies on the axis of the main body. Where the cutting edges of the cutting blades are arranged along the plurality of involutes, it is preferable that the cutting edges of each of the above-described at least one pair of inside and outside cutting blades are located in the same involute. As in the above-described assembly of mode (16), the plurality of bores for receiving therein the respective cutting blades may be located on a single circle, or alternatively on a plurality of circles having respective diameters different from each other.
(18) A cutter head assembly according to any one of modes (15)-(17), wherein the plurality of cutting blades includes an inside cutting blade and an outside cutting blade, the inside cutting blade cutting the workpiece by a portion of the cutting edge which portion is closer to the axis of the main body than the other portion of the cutting edge, the outside cutting blade cutting the workpiece by a portion of the cutting edge which portion is more distant from the axis of the main body than the other portion of the cutting edge.
The assembly of this mode (18) is advantageously used as a gear cutter for machining or cutting a bevel gear having curved teeth, wherein opposite side faces of a tooth slot of the bevel gear are satisfactorily formed by the inside and outside cutting blades, respectively.
(19) A cylindrical cutting blade having a first flat surface and a second flat surface formed as respective parts of an outer circumferential surface thereof and parallel to an axis of the cutting blade, the cutting blade further having, in one of axially opposite end portions thereof, a cutting edge defined by an intersection of a rake face and a flank face which are formed in the cutting blade.
The above-described second object may be achieved according to this mode (19). In the cylindrical cutting blade of this mode (19), the first and second flat surfaces may be formed to be parallel to each other or unparallel to each other. However, it is preferable that the second flat surface intersects with a plane that is perpendicular to the first flat surface and that contains the axis of the cutting blade. The present cylindrical cutting blade may include any one or any combinations of the features recited in modes (9)-(13).
(20) A cutter head assembly comprising:
a main body which has at least one cutting-blade receiving bore and at least one clamping-member receiving bore unparallel to the cutting-blade receiving bore and partially interfering with the cutting-blade receiving bore;
at least one cylindrical cutting blade each received in a corresponding one of the above-described at least one cutting-blade receiving bore, the cutting blade having two flat surfaces formed as respective parts of an outer circumferential surface thereof and having respective widths as measured in a direction parallel to a radial direction of the cutting blade, the two flat surfaces being parallel to each other and parallel to an axis of the cutting blade, the cutting blade further having a cutting edge in an axially distal end portion thereof which projects from an end face of the main body, the cutting edge being defined by an intersection of a flank face which is formed in the axially distal end portion, and a rake face which is formed in a widthwise intermediate portion of one of the two surfaces and which is parallel to the axis of the cutting blade; and
at least one cylindrical clamping member each received in a corresponding one of the above-described at least one clamping-member receiving bore and having a fitting portion and a cam portion, the cylindrical clamping member being rotatably fitted at the fitting portion in the clamping-member receiving bore, the cam portion having a cam surface whose radial distance from an axis of the fitting portion changes in a circumferential direction of the cylindrical clamping member.
The assembly of this mode (20) is advantageously used as a face milling or hobbing cutter for cutting a bevel gear having curved teeth, or alternatively as any other cutting tool for, for example, boring a bore, machining a flat surface and machining an outer circumferential surface. The present assembly may include any one or any combinations of the features recited in modes (4)-(8) and (12)-(14).
(21) A cutter head assembly comprising:
a main body which is to be rotated about an axis thereof and which has at least one cutting-blade receiving bore receiving therein a cutting blade, the cutting-blade receiving bore being offset from the axis and extending from an axially distal end face of the main body toward an axially proximal end face of the main body, the main body further having at least one clamping-member receiving bore unparallel to the cutting-blade receiving bore and partially interfering with the cutting-blade receiving bore; and
at least one cylindrical clamping member each received in a corresponding one of the above-described at least one clamping-member receiving bore and having a fitting portion and a cam portion, the cylindrical clamping member being fitted at the fitting portion in the clamping-member receiving bore, the cam portion having a cam surface whose radial distance from an axis of the fitting portion changes in a circumferential direction of the cylindrical clamping member,
wherein the cylindrical clamping member is rotatable about the axis of the fitting portion so that the cam surface is brought into contact with an outer circumferential surface of the cutting blade which is received in the cutting-blade receiving bore, for thereby pressing the cutting blade onto an inner circumferential surface of the cutting-blade receiving bore.
The cutting blade used for the assembly of this mode (21) may have any desired shape as long as the cutting blade is fittable into the cutting-blade receiving bore. The present assembly may include any one or any combinations of the features recited in modes (4)-(8) and (14)-(16).